Inboard and outboard devices (such as an inboard engine and an outboard drive) as an engine disposed in a ship body and an out-drive device that is disposed outside the ship body and receives force transmitted from the engine have conventionally been known (see, for example, Patent Literature 1). The out-drive device is a propulsion device that propels the ship body by rotating a screw propeller, and is also a steering device that turns the ship body by turning with respect to a traveling direction of the ship body.
A ship steering system for an out-drive device includes a hydraulic actuator and a hydraulic controller, in addition to the out-drive device described above. The ship steering system for an out-drive device further includes a ship steering device including a steering wheel, a joystick, and the like. In the ship steering system for an out-drive device, the hydraulic controller controls the hydraulic actuator in accordance with an operation on the ship steering device. The hydraulic actuator turns the out-drive device (see, for example, Patent Literature 2).
In conventional ship steering systems for an out-drive device, steering control through the hydraulic controller stops as soon as the hydraulic controller fails and is unable to control the hydraulic actuator. Thus, the conventional ship steering systems for an out-drive device have a problem that the steering is disabled as soon as the hydraulic controller fails and becomes unable to control the hydraulic actuator.